Self-assembly organizes chaotic units into ordered structures; simple biological units such as peptides have demonstrated this ability. The potential vast applications of peptide-based self-assembled nanostructures are due to their biocompatibility and other properties which include chemical, magnetic, optical and electronic. The fundamental understanding of the key structural features, such as intra and intermolecular forces involved, of the nanostructures could contribute substantial understanding of the properties and function of the materials. As a result, both noncovalent interactions and architecture of nanostructure could be tuned by changing the functional groups of the units.<br/>We hypothesized that the formation of a 3-D aromatic arrangement was due to π-π stacking between the aromatic phenyl rings and the hydrogen bonding between a donor and acceptor atoms of the cyclic phenylalanine-tyrosine dipeptides. We performed quantum chemical computational calculations in both gas and solvent (acetone) phases using several levels of theories such as density functional theory and Møller–Plesset perturbation theory. The structure, energetics, thermodynamics, and spectra of the lowest energy conformers were then analyzed. The lowest energy conformer was used to build dimer conformers in the stack, side by side and T-shaped arrangements. These were studied using density functional theory tight-binding method and several energy decomposition methods will be used to further analyze the interaction energies. These works confirmed that π-π stacking and hydrogen bonding are critical factors in the early self-assembly. We anticipate to further understand not just the intramolecular forces in a single cyclo(Phe-Tyr) and intermolecular forces in dipeptide unit, but also intermolecular forces between several dimer units which would assemble as a hexamer, and finally a nanotube itself.<br/>

Study of interactions in the early self-assembly of cyclic phenylalanine-tyrosine dipeptides

256th National Meeting (2018)

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